The terms HV for high voltage and LV for low voltage are abbreviations as used below.
Operation of HV components in vehicles may lead to dangerous operating states when plugs or connections become loosened or when parts carrying electric voltage can be touched by people. In addition, a sudden interruption in the HV connection may cause damage to components and/or to the vehicle system due to the development of electric arcs such as those which can occur when there is a sudden interruption in high electric currents, for example. Furthermore, loss of the HV power supply may result in a failure of the HV component such that the vehicle system no longer receives a return message for diagnostic purposes.
According to prior art, such an electrical safety lock is implemented, for example, by looping a low voltage (LV) signal for the HV part of each component and each device. All these loops together form a serial connection or linkage for the lock signal, also known as an interlock signal. Then when an HV plug is unplugged or has contact problems, the entire loop is opened and active system, for example, the vehicle system will detect this stat and can then initiate suitable measures. These measures may consist of, for example, completely shutting down the HV system of the vehicle. A known implementation uses short-circuit bridges in the cable trees of the HV power supply of the vehicle which keep the loops that are supplied with power, via the LV plug, closed. Another method uses short-circuit bridges in the HV plugs of the various HV devices. Such approaches are known in DE 10 2010 048 348 A1 and in DE 10 2009 053 113 A1. A number of disadvantages are associated with the known systems.
Due to the series connection of the individual HV components in a loop, an interruption of this loop in a single component may lead to the downfall of the entire HV system because the various links are associated to one another via a link. It is then no longer readily possible to diagnose which component caused the failure.
Another problem is that the interlock lines which are at LV potential have been installed close to the HV high-current lines, which can lead to crosstalk of electromagnetic interference with the LV system, which is not usually shielded and therefore can cause inferior EMC performance. Furthermore, simply shutting down the HV circuit in the vehicle is not a suitable means for protecting the individual HV components and/or devices from damage, e.g., due to the development of electric arcs or contact-breaking sparks.